Michael, you are comparing standard flooded dual purpose group 24 or group 27 batteries to an industrial grade absorbed glass mat battery that has the same capacity as 6 interstates and will be a much better deep cycle battery. It is like comparing a 17' bayliner with a 3.0 6 cylinder to a fully loaded xstar.

I have a pretty big system 3800 Watts rms. I ran it hard for 3.5 hours yesterday on just one of my 8D's and only lost 20% of the battery. If you have you have the space, as you say you do, get either the 4 or 8 and Lifeline is the best.